It does seem logical that Angelos received some compensation for a team moving into their market, so I don't really get the outrage over the original agreement. That seems like the norm for all sports leagues.
Here's the problem: this was NEVER their market at any period of time under MLB's rules and bylaws. The Orioles' existence was granted by an existing MLB team -- the Senators in the same league, who did get a ONE-TIME fee for not acting to gum up the works but did not have to cede some media rights that MLB had granted it. Thus, when the Senators left in 1971, the Orioles didn't automatically take over rights as have an open ticket to market to the large market to its southwest for as long as it could.
All of that was gravy they should have contended themselves with, especially when the DC/VA/MD grew by leaps and bounds in both population and average income, outstripping the Baltimore area in both. That an MLB team didn't come back to the national capital area for 33 years is all the more reason the Orioles should have been content with years without competition, plus the fact that the team that came went into the NL, meaning the Yanks, Sox, and other AL draws stayed largely exclusive to them other than some sporadic interleague play.
Here's the clincher: The Baltimore Orioles defined marketing area according to MLB bylaws includes Baltimore City and County and the counties touching Baltimore County. That's it. The Baltimore Orioles' cable broadcast area before MLB‘s return to its defined media market in metropolitan Washington had extended from the Pennsylvania border to North Carolina, and from Delaware to West Virginia; however, that broadcasting privilege was not and did not equate to a defined and exclusive broadcasting right for the Baltimore Orioles. During the 18 years of overlap of the Orioles and Senators, the latter's defined market included Montgomery County, Prince Georges County, the District, and Northern Virginia. Nothing transferred that northward, nor was there any precedent for considering it to be officially ceded just because the Senators were gone. Each previous Orioles ownership group before Angelos acting accordingly, stating that the only stipulation they would ask MLB to prioritize was to put a returned team in the NL.
What did that was an owner-turned-commish that ran from any sort of litigation (don't forget how long it took to get a team to move in large because of that) became caretaker of the Nats and of their sale. What that let Angelos do was try to bluff his way into being owed "rights", even though an internal MLB study from the early 2000s confirmed he was owed nothing. Selig didn't care, made a bad deal that any prospective owner had to sign on to in order to get the Nats, and that was that. And now MLB sits around and lets the team not be paid its monies for years on end. Pathetic.